The Old East Slavic (Old Russian) proper noun Русь is first recorded in the 12th-century Primary Chronicle. Older attestations of the same name in Greek, Latin and Arabic date to the 9th and 10th centuries.

And they went overseas to the Varangians, to the Rusĭ. These particular Varangians were known as Rusĭ, just as some are called Swedes, and others Normans and Angles, and still others Gotlanders, for they were thus named.

Русь ‎(Rusĭ) is the collective plural for the Varangian elite ruling Rus', the Old East Slavic state. A single individual is called a русинъ ‎(rusinǔ), whence modern Russian руси́н ‎(rusín, “Ruthenian”). While the Rus-Byzantine treaty of AD 911 is unclear on whether "Rus" refers just to the ruling elite or to the entire population, the treaty of 944 is explicit on the point that the "Rus" are "all people of the Rus land" (русьскаꙗ землꙗ ‎(rusĭskaja zemlja)).